The present invention relates to sliding doors and, more particularly, to heavy sliding doors such as those for vaults installed in banks.
Conventionally, most of such heavy doors as those for vaults of banks have been constructed as hinged doors having one or two door bodies adapted to be swung around the hinges when opened.
These hinged doors have fundamental drawbacks as listed below:
(1) A semicircular space centered at the hinge and of a radius equal to the length of the door body must be preserved. PA1 (2) A considerable manual force is required for opening and closing, when the door has been finished with a deteriorated precision. PA1 (3) A high precision is required for the installation of the door. If the door is not attached accurately, e.g. inclined forwardly, the door tends to open by itself, once opened slightly, causing a substantial danger for the operator. PA1 (4) In view of its purpose to express the safety of deposits and the reliability of the bank to the clients, the door of the vault is usually installed at a position easily seen by the clients. However, only the back side of the door is visible to the clients during the use of the vault, in the case of the hinged doors, which presents a poor appearance and, therefore, has less of a propaganda effect for the safety of the bank. PA1 (5) A complicated stepped structure is necessary at the contact area of the door with the wall of vault, for preventing fire and smoke from invading the vault. PA1 (6) The higher precision of construction and installation lead to a correspondingly higher cost of manufacture and installation.